Differential speed control mechanism



5y 152 H. CLARK 9 DIFFERENTIAL SPEED CONTROL MECHANISM Filed July '16, 1949 ENERGY suEsmNc SUPPLY FOR PR l HE MOVE R SERMO- RECEIVER PRIME WOVEN SERVO TRANSMITTER TO 60 CYCLE CONTROL l3 PUSH ALC-SUFFLY A E I MASTER CONTROL we CONTQOLLED DEVICE DEVIGE OPERATED A CONTROLLED FROBQ SPEED g PfiIME woven H4 El$ \fi/ MMVEMTQ. 1 E r mm m.

Patented July 8, 1952 DEFFERENTIAL SPEED CQNTRGL 1 MECHANISM i;

li ez zie' Clark, Houston, Tex.

. Application July 16, 1949, Serial No. 105,183

This; invention relates a prime mover automatically to attainand to maintain a predetermined constant speed irrespective of the load on the prime mover.

The rotativespeed of prime movers is commonly controlled by means of governors. The conventional type governors depend for their action upon centrifugal force and consist essentially of a pair of masses rotating about a spindle driven by the prime mover, the speed of which is to be controlled. These masses when rotated tend to fly outwardly and this outward motion is resisted by a controlling force such as a spring. With an increase in speed,the controlling force is overcome andthemasses move outwardly. This motion is transmitted to valves supplying the prime mover withits working fluid or fuel, reducing or increasing the supply of working fluid or fuel thereto, depending upon whether the speed of the prime mover is greater than or less than the desired speed. In the past, numerous types of governors have been suggested for controlling of speed of prime movers. Despite their widespread use, all governors permit hunting although this characteristic is less pronounced in some types of governors thanv in others. Furthermore, this tendency to permit hunting cannot be entirely eliminated and ccnsequently governors are not suitable for use where it is desired to accurately control the speed of :a prime mover. Also, the customary fly-weight types .of governors, when not hunting, fail tomaintainan accurate, predetermined speed with varying loads.

It is an object of this invention to provide a mechanism for causing a prime mover to attain and continuously to maintain a predetermined constant speed. A further object is to provide a mechanism for causing a prime mover to attain and continuously to maintain a predetermined constant speed irrespective of the load on the prime mover. It is another object of thepresent inventionto provide a mechanism for controlling the speed of a prime mover used for the generation of electric power;-

Briefly, the mechanism of my invention consistsof a master. control device operated at a constant'speed, a controlled device the speed of which is controlled by the prime mover, a differential gear assembly mechanically connecting the master control device and the controlled device and means actuated by the differential for translating the rotative motion of the differential to a valve or other mechanism which controls the supply of energy substance to the prime mover.

" Mprespecifically, the mechanism of my invention Claim. (01. 264;9)

to a device for causing comprises a differential drive, one axle of which is mechanically connected to a master control device operated at constant speed, the other axle Having briefly described the device of my invention, it will obvious that I have attained the objects hereinbefore set forth. Other objects and advantages of the present invention will be seen from a reading of the following detailed description taken in conjunction with the single figure of the drawing which is a diagrammatic showing of the device ofmy invention. V

Turning now specifically to the-drawing, it will be seen that individual parts are designated by numbers and groups of parts orassemblies are designated by letters, like numerals and like letters indicating corresponding parts and groups of parts respectively throughout.

A designates a master control device operated at constant speed fl; designates a device containing rotatable element, the speed of which is controlled by the energy supplied to prime mover C. l) designates a source of energy substance for prime "mover C, the nature ofsaid source being dependent upon the particular energysubstance required by prime mover C. E designates a mechanism .for controlling the supply of energy substance D to prime mover C. F designates a servo-trans- 7 mitter which may suitably be a Selsyn while G designates a servo-receiver which may also suitably be a Selsyn. J designates a first differential gear assembly while J designates a second difierential gear assembly; J and J may be properly regarded as a double differential gear assembly. K designatesa load control mechanism'.- Load control mechanism'K may suitably be of the. kind which is physically operated by an operator, 'for example a crank, or it may be a motor arranged to be actuated from time to time by an operator.

Differential gear assembly J consists of ring gear HI which is mounted coaxially on shaft H2 and isfreely rotatable on said shaft. Spider H3 is rigidly fastened to ring gear III at Hi.

Mounted Within spider I I3 is bevel gear l l 5, bevel gear H5 being free to rotate about its axis on pin ll 6 which is secured to spider I It. It will be, apparent, that a plurality of gears l I 5 may be mounted wi tnin spider H3 rather thansjust'bne such gear, as shown. One end of axle H2 terminates within spider H3 and has mounted on said end bevel gear III which meshes with the gears of bevel gear I I5. Spider I I3 also supports shaft II8, the axis of shaft II8 coinciding with the axis of shaft H2, the inner end H9 of shaft H8 being positioned internally of spider H3 and having mountedthereon for rotation therewith bevel gear I20, the gears of which mesh with the gears of bevel gear I I5. Shaft H2 is mechanically connected to rotating element 25 carried by master control device A while shaft H8 is me chanically connected to rotating element 26'of' controlled device B. Thus, shaft I I2 i arranged to rotate with rotating element 25 while shaft H8 is arranged to rotate with rotatable element 26.

Differential gear assembly J consists of ring gear I20 which is mounted coaxially on shaft I2I and is freely rotatable on said shaft. Spider I22 is rigidly fastened to ring gear I20 at I23.

Mounted within'spider I22 'is'b'e'v'el gear I24, bevel gear I24 being free to rotate aboutits axis-on pin I'25jwhich is'seclll'ed tdspidef I22. W111 be apparent that a plurality of gears I24 may be mounted within spider I22 rather than just the one gear, as shown. One end of a'Xle'IZI terminates within spider I22 and has inountedon said end for rotation with said shaft bevel gear I26 which'meshes with the gears of bevel gear I24. Spider I22 also supports shaft'I21, theaxis of shaft I2'I coinciding with the axis of shaft 121, the innerend I28 of "shaft I2! being 'posishaft I2I isworni gear |33.' Gear I33 meshes with worm I34 which is mechanically connected by means of shaft I35 to load control mechanism K, worm I34 being rotatableabout its axis when actuated by load control mechanism K.

Shaft 2|, which may suitably be affixed to a stationary member by means of journal 22 for rotation about its axis, carries on one end 23 thereof gear I36, gear I36 being so positioned that it meshes with ring gear I 20f Shaft 2Iis linkedl to energy substance control mechanism E by any suitable means. In the means illustrated, numeral 21 designates a clutch which may be of any suitable type for connecting shaft 2| to shaft 28, shaft 28 operating in conjunction with servo-transmitter F. Servotransmitter F and servo-receiver G are connected by means of leads 29, 30 and 30'. Servo-receiver G includes a suitable mechanism including member 3| for actuating energy substance controlling.

mechanism E. Member 3| is shown as linked to bell crank 32 which is adapted to be moved ,arcu- I through conduit 40, energy substance control mechanism E, and conduit 4| to prime mover C.

The operation of hereinbefore described mechanism will now be indicated. When master control device A and controlled device B are rotating at exactly the same speed, but in opposite directions, and when load control mechanism K is not actuated to rotate worm. I34 bevel gears H5, H1 and I20 of differential gear assembly J will also rotate but spider H3 and consequently gear III will remain stationary. Inasmuch as bevel gear III does not rotate, gear I3I, shaft I21, and gear I29 will also be stationary. Since worm I34 is not being rotated, worm gear I33, shaft I 2|, and bevel gear I26 will also remain stationary. Bevel gears I26 and I29 being stationary, bevel gear I24-is'also'stationary. In turn, this means thatspider I22 and ring gear I20 are stationary. Since gear I36 carried by shaft 2| can rotate only when ring gear I26 rotates, gear I36 and shaft 2| remain stationary. With these conditions prevailing, element 31 of energy substance control mechanism E will remain in fixed position, thereby permitting a fixed quantity or volume of energy substance D to flow to prime mover C. Y

The condition wherein controlled device B is rotating at exactly the same speed as master control device Aand no positional change has been gear l I I. Rotation of ring gear I I I, in turn, produces rotation of gear I3I, shaft I27, and bevel gear I23.- As already mentioned, worm gear I33 is stationary and'asa result shaft |2| and bevel gear I26 are also stationary. With bevel gear I26 stationary and bevel gear I29 rotating, bevel gear I24 also rotates while spider I22 and ring gear I20" are forced to rotate in cooperation with bevel gear I24. Since gear I36 is amxed to shaft 2| and meshes with ring gear I20, gear I 36 and shaft 2| rotate also. Withclutch 2'! mechanically connecting shaft 2| and shaft 28, rotation of shaft 2| is communicated through clutch 21 and shaft 28 to servo-transmitter F. Servo,- transmitter F, by reason of the rotation of shaft 23, transmits a signal by means of leads 29, 30, and 30 to servo-receiver G which, in turn, moves member 3| to the right or left, depending upon Whether device B is running faster or slower than device A. This movement is communicated through bell crank 32 to control element 31. If

controlled device B is rotating at a slower speed than control device A, control element 3? is moved in a direction to permit a larger quantity or vol.

ume of energy substance D to flow to prime mover C. If, on the other hand, controlled device B is rotating at a faster rate than control device A, control element 3'! acts to decrease the flow of energy substance D to prime mover C. This alteration of the quantity or volume of energy substance D to prime mover C correspondingly alters the speed of rotation of prime mover C which, in

turn, produces a corresponding change in speed of rotation of rotatable element 26 of controlled device B. When controlled device B attains exactly the same speed as control device A, the system will make no further adjustments in the rotative speed of prime mover C.

A third condition which may prevail will now be discussed. This third condition will exist when controlled device B and master control device A are rotating at exactly the same speed, but in opposite directions, and it is desired to increase or to decrease the load on prime mover C. As previously pointed out, when controlled device B and master control device A are rotating at exactly the same speed, spider H3 and ring gear III remain stationary. This means, in turn of course, that gear I3I, shaft I21 and bevel gear I29 are also stationary. It will be understood of course that in order to alter the load on prime mover C to the desired load, load control mechanism K must be actuated by an operator, this actuation in turn producing rotation of shaft I35 and worm 13d. Rotation of worm I34 causes corresponding rotation of worm gear I33, shaft I2I, and bevel gear I26. Since bevel gear I29 is stationary while bevel gear I26 rotates, bevel gear 128, spider I22 and ring gear I22 must rotate. Rotation of ring gear I29 of course produces corresponding rotation of gear I36 and shaft 2|. Rotation of shaft 2! is communicated through clutch 21 to shaft 28 and servo-transmitter F. Servo-transmitter F transmits this signal as hereinbefore described to energy substance control mechanism E. It will be understood, of course, that when it is desired to increase the load on prime mover C, load control mechanism K will be actuated by an operator so as to rotate worm I34 in one direction; when, on the other hand, it is desired to decrease the load on prime mover C, control mechanism K will be actuated so as to rotate Worm I34 in the opposite direction. If there is any tendency for the prime mover to alter its speed during a change in the positional setting of load control mechanism K, this tendency is corrected by means of differential gear assembly J as hereinbefore described.

Although load control device K is designed to alter or regulate the load on prime mover C by alteration of the supply of energy substance D thereto, no change in the speed of prime mover C, other than a transitory one, can be accomplished by changing the positional setting of load control mechanism K. The reason for this is that the speed of prime mover C is controlled by control device A and controlled device B. Should a change in the amount or volume of energy substance D supplied to prime mover C,

caused by a change in the positional setting of load control mechanism K, be sufiiciently great to cause a change in the speed of prime mover C, then control device A and controlled device B automatically return prime mover C to its nor mal speed, making it necessary to again adjust the load on prime mover C to its proper value by actuation of load control mechanism K.

The nature and objects of the present invention having been completely described and illustrated, what I wish to claim as new and useful and to secure by Letters Patent is:

Apparatus for maintaining the speed of a rotative prime mover substantially constant under conditions of both constant and varying loads on said prime mover comprising, in combination, a

primary differential gear assembly including a first and a second rotatable shaft coaxially arranged and a ring gear rotatable by said shafts when said shafts rotate at different speeds in opposite directions, a secondary differential gear assembly including a first and a second rotatable shaft coaxially arranged and a ring gear rotatable by said shafts when said shafts rotate at different speeds, said first shaft of said secondary differential gear assembly being mechanically connected to and rotatable by said ring gear of said primary difierential gear assembly, a master control device having a rotatable element rotated at a controlled constant speed mechanically connected to said first shaft of said primary diiferential gear assembly for rotating said shaft, a controlled device having a rotatable element the speed of which is controlled by said prime mover mechanically connected to said second shaft of said primary difierential gear assembly for rotating said shaft in the opposite direction from said first shaft of the primary differential gear assembly, physically operated means adapted to prevent rotation of said second shaft of said secondary differential gear assembly by said first shaft and also adapted to rotate said second shaft, a valve element for controlling the supply of energy substance to said prime mover and means coupling said valve element with the ring gear of said second differential assembly for transmitting the rotative motion of the ring gear of said secondary difierential gear assembly to said valve element for regulating the supply of energy substance to said prime mover.

HEZZIE CLARK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Germany June 25, 1910 

